This investigation is designed to utilize data from an existing cohort of 120,000 women, aged 30 to 55 in 1976, to study risk factors for myocardial infarction in women. Exposures to oral contraceptives, post-menopausal estrogens and cigarette smoking have been documented, as have menopausal status, a past history of hypertension, diabetes, angina pectoris and hypercholesterolemia, and family history of myocardial infarction. Retrospective data have been collected for the period prior to 1976, and prospective data, including dietary practices, are being collected biennially through 1982. Information is gathered by mail questionnaires, with further documentation of events by review of hospital records. Simple, stratified and multivariate analyses will all be employed to elucidate the separate relationships of the risk factors with myocardial infarction in women, in both retrospective and prospective data. Interactive effects will be emphasized in both data sets.